1. Field of the Invention
The invention relates to a projection system, more particularly to a projection system including a compact optical engine having enhanced heat dissipating efficiency.
2. Description of the Related Art
Conventional portable projection devices are developed in the trend of compactness to enhance portability thereof. However, compactness may entail certain disadvantages. Referring to FIGS. 1, 2 and 3, in a conventional projection device 1, light from a projector lamp 11 is directed into a housing 201 of an optical engine 2 for processing. The processed light is projected via a projection lens 20 disposed at a front end of the housing 201 onto a display screen 293. During operation, the projector lamp 11 and certain components of the optical engine 2 will generate high heat. This is because the projector lamp 11 emits concentrated light which generates a large amount of heat, and the light from the projector lamp 11 which is incident on an image synthesizing area 27 within the housing 201 also produces heat. The heat must be dissipated to cool the relevant components. Otherwise, the color of the images to be projected, as well as the distribution of the light, will be adversely affected or, worse still, the relevant components will be severely damaged. Therefore, in the conventional projection device 1, a first fan 12 is disposed adjacent to the projector lamp 11 for extracting the heat generated by the projector lamp 11 rearwardly, and a second fan 21 is disposed at a bottom portion of the housing 201 for drawing cool air from below into the image synthesizing area 27 to dissipate the heat via a top portion of the housing 201 so as to lower the temperature of the image synthesizing area 27 within the housing 201. Operating power for the entire projection device 1 is supplied by a power supply unit 13 which is located in front of the projector lamp 11 and adjacent to the housing 201 in order to facilitate supply of power to the projector lamp 11 and the electronic circuits of the projection device 1. As the power supply unit 13 also produces heat during operation, and as the heat produced thereby cannot be effectively drawn out by means of the first fan 12 which is disposed to dissipate the heat generated by the projector lamp 11 and which is located at a relatively far position, a third fan 29 is provided adjacent to the power supply unit 13 to draw in cool air so as to ensure good heat dissipation.
During operation, light from the projector lamp 11 is guided into the housing 201 of the optical engine 2. A filter 22 is disposed in the housing 201 adjacent to a rear end of the housing 201 to filter the ultraviolet and infrared light components of the light from the projector lamp 11, thereby permitting passage of only white light therethrough. The white light passes through a pair of spaced-apart light integrator lenses 23 for conversion into evenly distributed light that subsequently passes through a polarization state converter 24. The polarized light is thereafter reflected by a mirror 25, and passes through two spaced-apart light splitters 261, 262, which split the white light into first, second and third color components (e.g., red, green and blue color components) that continue to proceed to the image synthesizing area 27. The first, second and third color components respectively reach first, second and third liquid crystal light valves 271, 272, 273 in the image synthesizing area 27 for light modulation. The modulated first, second and third color components are recombined by a light synthesizing prism 274 into an image beam, which is subsequently projected via the projection lens 20 onto the display screen 293.
In the conventional projection device 1 as described above, during light modulation of the first, second and third color components, since the light incident on the first, second and third light valves 271, 272, 273 is intense and generates high heat, and since relevant components like the liquid crystal components and polarizers within the housing 201 are vulnerable to high heat, an undue rise in temperature will result in abnormal operation and inferior color presentation, or even damage to the components. Therefore, a good heat dissipation system is needed. The second fan 21 described above is intended for this purpose and is mounted on the bottom portion of the housing 201 below the light valves 271, 272, 273 to dissipate heat.
With further reference to FIG. 2, the optical components that are disposed inside the optical engine 2 to process the light from the projector lamp 11 define a device axis 291. The projection lens 20 defines an image axis 292 that is offset from and that is at a slightly higher level than the device axis 291 so that the image beam is projected therefrom upwardly to achieve a projection effect such as that illustrated in FIG. 3, in which the light projected by the projection lens 20 onto the display screen 293 disposed vertically in front covers a projection field 294 that has a large portion located above the image axis 292 to facilitate viewing by a seated audience at eye level.
Given the aforesaid, the provision of the second fan 21 at the bottom portion of the housing 201 of the optical engine 2 increases the vertical thickness of the optical engine 2 and is therefore detrimental to the compactization of the projection device 1 as a whole.
In addition, since the second fan 2 draws a current of cool air upwardly in a single direction to dissipate the hot air inside the optical engine 2, an air vent has to be provided in the top portion of the housing 201. If the user inadvertently places an object, such as a document, on top of the housing 201 to thereby block the air vent, the light valves 271, 272, 273 and other components may overheat and become damaged.
Therefore, the primary object of the present invention is to provide an optical engine for use in a projection system, which is compact and which can enhance heat dissipating efficiency.
Another object of the present invention is to provide a projection system incorporating the aforesaid optical engine so as to overcome the above-mentioned drawbacks associated with the prior art.
According to one aspect of the present invention, an optical engine of this invention includes:
a housing having upper and lower surfaces, and front and rear ends;
a light splitting unit disposed in the housing adjacent to the rear end and adapted to split white light that enters the rear end of the housing into first, second and third color components;
first, second and third light modulators accommodated within the housing between the front and rear ends for respectively modulating the first, second and third color components received from the light splitting unit;
a color synthesizing prism disposed in the housing adjacent to the first, second and third light modulators for recombining the first, second and third color components modulated by the first, second and third light modulators to form an image beam;
a projection lens disposed at the front end of the housing and adapted to project the image beam onto a display screen; and
a fan unit mounted on the upper surface of the housing, the fan unit having an inlet port facing toward the first, second and third light modulators for drawing air upwardly so as to dissipate heat generated by the first, second and third light modulators, the fan unit further having an outlet port that is transverse to the inlet port for discharging the air drawn into the inlet port.
According to another aspect of the present invention, a projection system of this invention includes:
a housing having upper and lower surfaces, and front and rear ends;
a light source disposed adjacent to the rear end of the housing and operable so as to supply white light;
a light splitting unit disposed in the housing adjacent to the rear end for splitting the white light from the light source into first, second and third color components;
first, second and third light modulators accommodated within the housing between the front and rear ends for respectively modulating the first, second and third color components received from the light splitting unit;
a color synthesizing prism disposed in the housing adjacent to the first, second and third light modulators for recombining the first, second and third color components modulated by the first, second and third light modulators to form an image beam;
a projection lens disposed at the front end of the housing and adapted to project the image beam onto a display screen;
a power supply unit disposed on one side of the housing adjacent to the light source to supply power to the projection system;
a first fan unit mounted adjacent to the light source to draw hot air away from the light source; and
a second fan unit mounted on the upper surface of the housing, the fan unit having an inlet port facing toward the first, second and third light modulators for drawing air upwardly so as to dissipate heat generated by the first, second and third light modulators, the second fan unit further having an outlet port that is transverse to the inlet port for discharging the air drawn into the inlet port toward the power supply unit such that the air from the second fan unit can carry hot air around the power supply unit toward the light source for extraction by the first fan unit.